Refining of copper



Patented Sept. 30, 1930 UNITED STATES, PATENT 1 OFFICE HARRY H.ALEXANDER, OF WESTFIELD, NEW JERSEY nnrmme or corrEa No Drawing.

impurities. In the furnace refining of cop-- per as heretofore moregenerally practiced, the metal and its impurities are melted. The moltenmaterial is suitably aerated to oxidize the impurities, some of whichpass OK as vapors and gases, While others pass into the slag forming onthe top, of the molten copper. In the case of sulfur and/or itscompounds, the sulfur is in part volatilized and in part converted tosulfur dioxide which passes off as a gas.

The aeration of the molten material is effected in various ways. Theolder method is to flap the top surface of the molten material with arabble, while admitting air into the refining furnace, in order tosubject the impurities to the oxidizing effect of the air. A latermethodis to pass air, under pressure, into the body of molten material. Theremoval of sulfur and/or its compounds is accomplished with considerabledifficulty, and a large excess of air must therefore be employed in therefining operation. Both methods have the desirable effect of oxidizingimpurities, but the very undesirable eflect of also oxidizingappreciable amounts of the copperfrequently as much as 6%. I

The oxidized copper must then be subjected to a deoxidizing or reducingoperation to obtain a relatively pure copper product. This latterrefining or reducing operation is conducted in various ways, generallyby the introduction into the body of molten copper of a suitablereducing agent, such as Wooden poles or carbonaceous materials. I

In the case of the usual copper to be refined, the removable impuritiesother than sulfur will pass out of the aerated copper Application filedJuly 5, 1928. Serial No. 290,703.

bath in about two hours. The'end'of this stage of the refining operationmay be determined by noting when the formation of slag appears to cease.About two hours more aeration are required to drive out the sulfur.

As a result of my investigations I have determined that the aeration orscorification action may advantageously be terminated before theconversion of appreciable amounts of copper to copper oxide has takenplace. he removable impurities present in the molten copper not oxidizedor removed by the air treatment may be suitably removed in accordanceWiththe practice of my invention.

In the practice ofthepresent invention, copper contaminated with sulfurand/or its compounds and the like maybe'refined without oxidizing thecopper, and the customary deoxidizing or reducing step may therefore beavoided. Or, the invention may be practiced in such a way as todesulfurize the copper while oxidizingsome of the copper, but at amaterial saving in time over what the prior practice requires.

According to my invention, a body of molten copper contaminated withsulfur and/or itscompounds, hereafter to be referred to as sulfur, andthe like is subjected to the action of steam, preferably dry steam underpressure, whereby the copper is desulfurized.

Steam at thetemperatures employed has the advantage of not oxidizing themolten copper, while at the same time oxidizing the sulfur to formsulfur dioxide gas. Steam, moreover, tends to drive out residual sulfur,as well as other removable impurities present in the copper bath. Thesteam is preferably superheated in order to dry the same.

When the contaminating sulfur is present as copper sulfide, the reactionresults in the formation of copper and sulfur dioxide gas, in accordancewith the reaction:

This reaction, moreover, has the advantage of forming free hydrogenwhich has the capacity for taking up free oxygen that may be presentabove the copper to be refined. So

long as the reaction takes place and hydrogen is being evolved, thisfree oxygen present above the copper cannot exercise an oxidizing effecton the copper. Hence, the formation of copper oxide is prevented. Theprevention of the formation of copper oxide can be conducted in thismanner, however, only i so long as there is sufiicient sulfur to keep ongenerating hydrogen until all of the free oxygen has been taken up. Incase the above re action goes to completion, any free oxygen that hasnot been taken up bythe hydrogen becomes available as an oxidizing agentfor the copper. Copper oxide then results,

This situation applies with equal force to' the gaseous conditionmaintained above the copper bath. Even though the formation'ofcopperbxide should be prevented within the copper bath, the maintenanceof oxidizing conditions above the bath will result in the formation ofcopper oxide. This may or may not be avoided, as desired.

The invention may be practiced in various ways. Thus, the molten copperwithin the refining furnace may first be subjected to the usual airblast or rabbling o 'eration in order to oxidize substantially al of theimpurities. That is to say, the aeration or scorification treatment maybe conducted until all of the removable impurities, except some sulfur,have been taken out of the copper bath.

The introduction of air is terminated at that oint, which may bedetermined by observmg when the formation of slag begins'to cease. Thecopper bath will still contain ap- 1 the copper bath.

. Anot er procedure is to subject themolten material in the refiningfurnace to the steam treatment of the invention'in order to take out allsuch impurities as are removable by steam at the temperatures employed.Moreover, the steam treatment may be conducted until the sulfur has beenremoved. The desulfurized copper bath may then be subjected, ifnecessary, to the usual air blast in order to remove any remainingimpurities. In this manner,the'oxidation of copper may be kept down to aminimum, particularly if a nonoxldizing atmosphere is again maintained aabove the copper bath.

It will, of course, also be apparent that the use of steam and the useof air may be alternated, as seen fit in the refining operation. In someinstances, the refining operation may also lend itself to the practiceof subjecting both steam and air, separately but simultaneously, or amixtureof steam and air, into the copper bath. Such a procedure may beparticularly advanta eous if it is desired to materially decrease t etime for performing the refining operation, and where there is noparticular concern as to the production of a final copper product thatis relatively free of copper oxide. Various other modifications of thepractice of the invention may, of course, be resorted to, but it is tobe understood that the omission of a discussion of them is not to beregarded as otherwise restrictive of the scope of the invention.

The apparatus usually employed to inject air into copper refiningfurnaces may advantageously employed for the introduction of steam intothe metal bath. In order that a 'thorough distribution of the steam maybe effected throughout the body of the molten material, it is advisableto introduce steam into the molten bath at a plurality of points,

referably near the bottom of the refining urnace. Since it is preferredto use dry steam, the pipes leading from the source of steam to therefining furnace should be insulated to minimize condensation of steam.Special injectors may, of course, be provided for steam alone.

In case it is desiredto inhibit the formation of copper oxide, theopenings leading into the furnace shouldbe tightly closed to prevent theingress of air. In other words, a non-oxidizing atmosphere should beprovided above the metal batli. Reducing gases may of course bemaintained above the metal bath. A molten protecting cover, such asdescribed and claimed in my copending application, Serial No. 123,886,filed July 21, 1926, of which this application is a continuation inpart, may advantageously be employed to protect the molten, bath fromoxidizing influences during the steaming treatment. According to saidcopending application a molten protective cover is contemplated thatconsists at least in part of soda glass having a melting point nothigher, and preferably lower, than that of the copper.

In case it is not desired to inhibit the formation of copper oxide, anoxidizing atmosphere may, of course, be maintained above the metal bath.The highly heated molten copper at the top of the metal bath then con-.tacts with the oxygen of the airand copper oxide is formed. The use ofsteam instead of air, particularly at the end of the refining operation,is nevertheless advantageously resorted to in order to driveout thesulfur. Even though cop er oxide has been formed, the time of therefining operation will be materially reduced over that heretofore generrequired.

all

Ifivenin the case ofdesulfurization with a1r, some of. the sulfurdioxide gases tend to be occluded in, or are retained by, the moltencopper. When an excessive amount of air is made to rise through the bodyof molten copthe other hand, not only inhibits the formation of copperoxide, but also effectively drives out these sulfur dioxide gases.

It will thus be seen that in the practice of this invention, it ispossible to effectively remove the chief impurity of copper, sulfur,Without oxidizing the copper, or at least oxidizing a. minimum of copperif that is desirable. The practice of-the invention, more-' over, hasthe advantage of removing otherimpurities. In the instances where it isnot desired to inhibit the formation of copper oxide, the refiningoperation contemplated by the invention may be conducted in much lesstime, thereby effecting a very important economy.

I claim:

1. The method of refining copper which comprises maintaining asubstantially nonoxidizing atmosphere above the copper in the form of amolten bath while subjecting the molten copper to the action of steamunder pressure, said steam being introduced into the body of moltencopper, whereby the copper is desulfurized and the formation of copperoxide is inhibited.

2. The method of refini g copper containinr an appreciable amoi nt ofsulfur as at least one of the-contaminating impurities, which comprisesaerating the copper while in a molten state,- said aerating operationbeing continued until the formation of slag ceases, and then introducingsteam under pressure into the body of molten copper to complete therefining operation.

3. The method of refining copper which comprises maintaining a moltenprotective cover consisting at least inpart of soda glass having amelting pointnot higher than that of the copper over the copper bath,and introducing steam under pressure into the body of molten copper. a

4. The method of refining copper which comprises aerating the moltencopper partially to remove nnpurities, maintaining a molten protectivecover consisting at least in part of soda glass having a melting pointnot higher than that of the copper over the partially refined copper,and then introducing steam under pressure into the body of moltencopper.

5. lhe method of refining copper which comprises aerating molten copperpartially to remove impurities, then providing a substantiallynon-oxidizing atmosphere above the copper bath, and introducing steamunder pressure into the body of molten copper.

6. The method of refining copper containing sulfur as at least one ofthe contaminants which comprises maintaining an oxidizing atmosphereover the copper bath, introducing steam under pressure into the body ofmolten copper until only a relativelysmall amount of sulfur remains,then providing a substantially non-oxidizing atmosphere over the copperbath, and introducing further amounts of steam under pressure into thebody of partially refined copper to complete the refining operation.

7. The method of refining copper containing an appreciable amount-ofsulfur as at least one of the contaminating impurities which comprisessubstantially sealing the furnace in which the refining operation isconducted against the seepage of outside air, and subjecting the copperin the form of a molten bath to the action of steam under pressurewhereby the copper is desulphurized and the formation of copper oxide isinhibited.

8. The method of refining copper containing sulfur as at least one ofthe contaminants which comprises maintaining an oxidizing atmosphereover the copper bath by permitting the seepage of outside air into thefurnace in which the refining operation is conducted, introducing steamunder pressure into the body of molten copper until only a relativelysmall amount of sulfur remains, then providing a substantiallynon-oxidizing atmosphere over the copper ath by sealing the furnaceagainst the entrance of outside air, and introducing further amounts ofsteam under pressure into the body of partially refined copper tocomplete the refining operation;

In testimony whereof I affix my signature.

HARRY H. ALEXANDER. I

